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[mlir][IntRangeInference] Handle ceildivsi(INT_MIN, x > 1) as expected #116284

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Merged
merged 3 commits into from
Nov 15, 2024
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[mlir][IntRangeInference] Handle ceildivsi(INT_MIN, x > 1) as expected #116284

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[mlir][IntRangeInference] Handle ceildivsi(INT_MIN, x > 1) as expected
krzysz00 Nov 14, 2024
62639eb
Make one of the constants a with_bounds to prevent folding
krzysz00 Nov 14, 2024
3827aab
Forgot to delete the old constant
krzysz00 Nov 14, 2024
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9 changes: 9 additions & 0 deletions mlir/lib/Interfaces/Utils/InferIntRangeCommon.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -375,6 +375,15 @@ mlir::intrange::inferCeilDivS(ArrayRef<ConstantIntRanges> argRanges) {
result.sadd_ov(APInt(result.getBitWidth(), 1), overflowed);
return overflowed ? std::optional<APInt>() : corrected;
}
// Special case where the usual implementation of ceilDiv causes
// INT_MIN / [positive number] to be positive. This doesn't match the
// definition of signed ceiling division mathematically, but it prevents
// inconsistent constant-folding results. This arises because (-int_min) is
// still negative, so -(-int_min / b) is -(int_min / b), which is
// positive See #115293.
if (lhs.isMinSignedValue() && rhs.sgt(1)) {
return -result;
}
return result;
};
return inferDivSRange(lhs, rhs, ceilDivSIFix);
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13 changes: 13 additions & 0 deletions mlir/test/Dialect/Arith/int-range-interface.mlir
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Expand Up @@ -249,6 +249,19 @@ func.func @ceil_divsi(%arg0 : index) -> i1 {
func.return %10 : i1
}

// CHECK-LABEL: func @ceil_divsi_intmin_bug_115293
// CHECK: %[[ret:.*]] = arith.constant true
// CHECK: return %[[ret]]
func.func @ceil_divsi_intmin_bug_115293() -> i1 {
%cIntMin_i64 = arith.constant -9223372036854775808 : i64
%cDenom_i64 = arith.constant 1189465982 : i64
%cRes_i64 = arith.constant 7754212542 : i64
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@Hardcode84 Hardcode84 Nov 14, 2024

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General comment: this check doesn't look very reliable, as this folding can be result from both int-range-optimizations and just usual folding. We probably should use with_bounds everywhere.

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@krzysz00 krzysz00 Nov 14, 2024

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Point, I can change it (though I do know this one doesn't constant-fold)

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@Hardcode84 Hardcode84 Nov 14, 2024

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Wait, intMin_i64 is not used?

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@krzysz00 krzysz00 Nov 14, 2024

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... hold on, wait what? How'd my local run pass? Checking again.


%0 = arith.ceildivsi %cIntMin_i64, %cDenom_i64 : i64
%1 = arith.cmpi eq, %0, %cRes_i64 : i64
func.return %1 : i1
}

// CHECK-LABEL: func @floor_divsi
// CHECK: %[[true:.*]] = arith.constant true
// CHECK: return %[[true]]
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